The present invention relates to a battery charging unit for an electrical or electronic device, particularly, although not exclusively, for a cellular radio telephone.
Commonly, portable cellular radio telephones are provided with removable batteries as their current source. Typically, these batteries are Nickel-Cadmium (Ni--Cd) batteries which are rechargeable.
To recharge the battery, the battery is left attached to the cellular radio telephone, and is recharged "in situ" by means of a charging unit. The charging unit is coupled to a mains alternating current (AC) supply via a conventional plug arrangement (in the United Kingdom, this is a 3-pin arrangement well known to persons skilled in the art), and is coupled to the battery via a multi-conductor cable to the telephone and through internal circuitry, to the battery to be recharged. Respective matching contacts are provided, on the casing of the telephone and in a plug terminating the free end of the cable, to couple current to the telephone and battery. The charger, typically, may be a simple transformer/constant current generator or switch mode power supply, as is well known to persons skilled in the art. The telephone may be provided with control logic and means to sense one or more parameters, for example battery temperature, these being indicative of the charge state of the battery. By monitoring such parameters, one is able to ensure that the battery is optimally recharged. With this method of recharging, the battery is "fast-charged", that is where a constant current of, for example, 600 -1000 mA is supplied to the battery to effect recharging. The telephone can still be used whilst the battery is being recharged.
A problem with storing these chargers is that the cable becomes entangled with other objects and is difficult to store. The user usually has to somehow wrap the cable - usually around the main body of the charging unit which can make it bulky. Commonly, during storage, this cable comes unwrapped and tangled, which can be fiddly and time consuming to untangle.
Among the many accessories available for portable cellular radio telephones, are so-called "travel chargers". These take the form of a charging unit incorporating a transformer/constant current generator, with a pin arrangement for coupling it to the mains supply. The casing for the charging unit is provided with a recess for receiving a spare battery. Contacts are provided within the recess for contacting matching contacts on the battery. A "trickle" current is supplied to the battery when the charging unit is coupled to the mains supply, thereby slow charging the battery received therein. The charging unit does not incorporate control logic for controlling fast charging, and therefore, is only capable of slow-charging a spare battery. This takes some time. There is the problem, therefore, that should the battery currently being used as the power supply for the telephone become discharged before the spare battery is recharged, then the telephone is out of operation. Unfortunately, when the recess may be perfectly located when using a wall mounted socket, should a floor mounted socket or any type of horizontally arranged socket be used, the recess may then be at such an angle that the battery will not stay in the recess or, if it does, does not make contact with the contacts properly, making charging impossible.
According to the present invention, there is provided a battery charging unit comprising a housing having a current supply means provided therein for supplying current to an electrical or electronic apparatus located remote from the battery charging unit, coupling means provided on the housing for coupling the current supply means to a mains power supply, means for coupling the remote apparatus to the current supply means, comprising a cable, and a reel provided in the housing for storing the cable in the housing when the battery charging unit is not in use, and allowing the cable to be dispensed when required. This has the advantage that by having a device around which the cable remains wound during storage and from which the cable is simply unwound from the charging unit when it is required eliminates the unsightly and messy bunching of the cable which is a feature of known charging units.
Preferably, the reel of the charging unit is not rotatable, and may be mounted within the casing and able to be pulled out of the casing to enable the user to manually wind the cable around the reel. Preferably the outside reel face comprises an opening means by which the user can grip the reel and pull it out of the casing when it is desired to wind or unwind the cable around the reel. Preferably, all of the cable or a part of the cable may be unwound, according to a user's requirements, and the casing may be closed when the desired amount of cable is unwound. Preferably the cable may exit the casing through an aperture in the casing.
Preferably the reel includes a spindle which is mounted in a spindle housing in which the spindle can be telescopically moved and at the same time maintained in the central position with respect to the casing. The spindle and the spindle housing preferably comprise corresponding stop means to stop further movement of the reel and a cammed detent means to resiliently retain the reel in the pulled out position. The detent means will provide sufficient retaining force on the reel so that the user has his hands free to hold the casing with one hand and wind or unwind the cable around the reel with the other without inadvertently pushing the reel back in the casing and yet low enough that when the winding operation is complete the user may press the reel back in the casing with sufficient force to overcome the cammed detent means.
Preferably, the battery charging unit comprises a releasably attachable cover, which is detachable by a user to reveal a non-rotatable reel enclosed by the casing. Preferably cover attaching means are provided, and preferably the cover attaching means comprise a snap-fit attaching means. The cover attaching means may comprise a locking means such as a press-release locking means. Preferably, the transformer/current generator components of the battery charging unit are arranged under the reel.
Alternatively, the cover may be permanently attached to said battery charging unit by means of a hinge, and the cover is openable by a user to reveal the reel thereunder.
Alternatively, the cover may be permanently attached to said battery charging unit, and slidable between a closed position and an open position in which the cover is moved and the reel is revealed thereunder. Preferably a plug at the free end of the cable fits under the closed cover when the battery charging unit is not in use. An aperture may be provided in the cover, through which the cable exits the battery charging unit. Preferably, the cover is provided with locking means to retain the cover in the closed position when the battery charging unit is not in use, and finger grips which are pressed inwards by a user to disengage said locking means.